2.1 问题
本案例练习对库、表、记录的基本管理，具体操作如下：
使用mysql命令连接数据库
练习库管理命令（查看、删除、创建库、切换）
练习表管理命令（查看、删除、创建表）
练习记录管理命令（插入、查看、修改、删除）
表－1 测试用表数据
2.2 步骤
实现此案例需要按照如下步骤进行。
步骤一：使用mysql命令连接数据库
连接MySQL服务器时，最基本的用法是通过 -u 选项指定用户名、-p指定密码。密码可以写在命令行（如果不写，则出现交互，要求用户输入），当然基于安全考虑一般不推荐这么做：
[root@dbsvr1 ~]# mysql -uroot -p123456 //紧挨着选项，不要空格
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 16
Server version: 5.7.17 MySQL Community Server (GPL)
Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> exit //退出已登录的mysql> 环境
Bye
默认情况下，msyql命令会连接本机的MySQL服务。但在需要的时候，可以通过 -h 选项指定远程主机；
[root@dbsvr1 ~]# mysql -h 127.0.0.1 –u root –p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 17
Server version: 5.7.17 MySQL Community Server (GPL)
Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> exit //退出已登录的mysql环境
Bye
步骤二：练习查看/删除/创建库的相关操作
以root用户登入“mysql> ”环境后，可以执行各种MySQL指令、SQL指令。基本的用法事项如下：
操作指令不区分大小写（库名/表名、密码、变量值等除外）。
每条SQL指令以 ; 结束或分隔。
不支持 Tab 键自动补齐。
\c 可废弃当前编写错的操作指令。
1）查看现有的库
mysql> show databases; //查看现有的库
+--------------------+
| Database |
+--------------------+
| information_schema | //信息概要库
| mysql | //授权库
| performance_schema | //性能结构库
| sys | //系统元数据库
+--------------------+
4 rows in set (0.15 sec)
2）切换/使用指定的库
mysql> use sys; //切换到sys库
Database changed
mysql> select database(); //确认当前所在的库
+------------+
| DATABASE() |
+------------+
| sys |
+------------+
1 row in set (0.00 sec)
切换到mysql库：
mysql> use mysql; //切换到mysql库
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select database(); //确认当前所在的库
+------------+
| DATABASE() |
+------------+
| mysql |
+------------+
1 row in set (0.00 sec)
5 rows in set (0.00 sec)
3）新建名为newdb的库，确认结果：
mysql> create database newdb; //新建名为newdb的库
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mydb | //新建的mydb库
| mysql |
| newdb | //新建的newdb库
| performance_schema |
| sys |
+--------------------+
6 rows in set (0.00 sec)
4）删除指定的库
mysql> drop database newdb; //删除名为newdb的库
Query OK, 0 rows affected (0.01 sec)
mysql> show databases; //确认删除结果，已无newdb库
+--------------------+
| Database |
+--------------------+
| information_schema |
| mydb |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
步骤三：练习查看/删除/创建表的相关操作
1）查看指定的库里有哪些表
查看mysql库里有哪些表：
mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+---------------------------+
| Tables_in_mysql |
+---------------------------+
| columns_priv |
| db |
| engine_cost |
| event |
| func |
| general_log |
| gtid_executed |
| help_category |
| help_keyword |
| help_relation |
| help_topic |
| innodb_index_stats |
| innodb_table_stats |
| ndb_binlog_index |
| plugin |
| proc |
| procs_priv |
| proxies_priv |
| server_cost |
| servers |
| slave_master_info |
| slave_relay_log_info |
| slave_worker_info |
| slow_log |
| tables_priv |
| time_zone |
| time_zone_leap_second |
| time_zone_name |
| time_zone_transition |
| time_zone_transition_type |
| user | //存放数据库用户的表
+---------------------------+
31 rows in set (0.00 sec)
2）查看指定表的字段结构
当前库为mysql，查看columns_priv表的结构，以列表形式展现：
mysql> desc columns_priv\G //查看表结构，以列表形式展现，末尾不用分号
*************************** 1. row ***************************
Field: Host
Type: char(60)
Null: NO
Key: PRI
Default:
Extra:
*************************** 2. row ***************************
Field: Db
Type: char(64)
Null: NO
Key: PRI
Default:
Extra:
*************************** 3. row ***************************
Field: User
Type: char(32)
Null: NO
Key: PRI
Default:
Extra:
*************************** 4. row ***************************
Field: Table_name
Type: char(64)
Null: NO
Key: PRI
Default:
Extra:
*************************** 5. row ***************************
Field: Column_name
Type: char(64)
Null: NO
Key: PRI
Default:
Extra:
*************************** 6. row ***************************
Field: Timestamp
Type: timestamp
Null: NO
Key:
Default: CURRENT_TIMESTAMP
Extra: on update CURRENT_TIMESTAMP
*************************** 7. row ***************************
Field: Column_priv
Type: set('Select','Insert','Update','References')
Null: NO
Key:
Default:
Extra:
7 rows in set (0.01 sec)
查看columns_priv表的结构，以表格形式展现：
mysql> desc columns_priv; //查看表结构，以表格形式展现末尾需要有分号
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
| Host | char(60) | NO | PRI | | |
| Db | char(64) | NO | PRI | | |
| User | char(32) | NO | PRI | | |
| Table_name | char(64) | NO | PRI | | |
| Column_name | char(64) | NO | PRI | | |
| Timestamp | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| Column_priv | set('Select','Insert','Update','References') | NO | | | |
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
7 rows in set (0.00 sec)
上述操作中，当引用非当前库中的表时，可以用“库名.表名”的形式。比如，切换为mysql库再执行“desc columns_priv;”，与以下操作的效果是相同的：
mysql> desc mysql.columns_priv;
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
| Host | char(60) | NO | PRI | | |
| Db | char(64) | NO | PRI | | |
| User | char(16) | NO | PRI | | |
| Table_name | char(64) | NO | PRI | | |
| Column_name | char(64) | NO | PRI | | |
| Timestamp | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| Column_priv | set('Select','Insert','Update','References') | NO | | | |
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
7 rows in set (0.00 sec)
3）在test库中创建一个名为pwlist的表
包括name、password两列，其中name列作为主键。两个字段值均不允许为空，其中密码列赋予默认空值，相关操作如下所述。
切换到mydb库：
mysql> use mydb;
Database changed
新建pwlist表：
mysql> create table pwlist(
-> name char(16) not null,
-> password char(48)default '',
-> primary key(name)
-> );
Query OK, 0 rows affected (0.38 sec)
确认新创建的表：
mysql> show tables;
+----------------+
| Tables_in_mydb |
+----------------+
| pwlist | //新建的pwlist表
+----------------+
1 rows in set (0.01 sec)
查看pwlist表的字段结构：
mysql> desc pwlist;
+----------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------+------+-----+---------+-------+
| name | char(16) | NO | PRI | NULL | |
| password | char(48) | YES | | | |
+----------+----------+------+-----+---------+-------+
2 rows in set (0.01 sec)
4）删除指定的表
删除当前库中的pwlist表：
mysql> drop table pwlist;
Query OK, 0 rows affected (0.01 sec)
确认删除结果：
mysql> show tables;
Empty set (0.00 sec)
5）在mydb库中创建一个学员表
表格结构及数据内容如表-1所示。
在MySQL表内存储中文数据时，需要更改字符集（默认为latin1不支持中文），以便MySQL支持存储中文数据记录；比如，可以在创建库或表的时候，手动添加“DEFAULT CHARSET=utf8”来更改字符集。
根据上述表格结构，创建支持中文的student表：
mysql> CREATE TABLE mydb.student(
-> 学号 char(9) NOT NULL,
-> 姓名 varchar(4) NOT NULL,
-> 性别 enum('男','女') NOT NULL,
-> 手机号 char(11) DEFAULT '',
-> 通信地址 varchar(64),
-> PRIMARY KEY(学号)
-> ) DEFAULT CHARSET=utf8; //手工指定字符集，采用utf8
Query OK, 0 rows affected (0.31sec)
查看student表的字段结构：
mysql> DESC mydb.student;
+--------------+-------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------------+------+-----+---------+-------+
| 学号 | char(9) | NO | PRI | NULL | |
| 姓名 | varchar(4) | NO | | NULL | |
| 性别 | enum('男','女') | NO | | NULL | |
| 手机号 | char(11) | YES | | | |
| 通信地址 | varchar(64) | YES | | NULL | |
+--------------+-------------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
查看student表的实际创建指令：
mysql> SHOW CREATE TABLE mydb.student;
+---------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|Table |Create Table |
+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| student | CREATE TABLE `student` (
`学号` char(9) NOT NULL,
`姓名` varchar(4) NOT NULL,
`性别` enum('男','女') NOT NULL,
`手机号` char(11) DEFAULT '',
`通信地址` varchar(64) DEFAULT NULL,
PRIMARY KEY (`学号`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
注意：若要修改MySQL服务的默认字符集，可以更改服务器的my.cnf配置文件，添加character_set_server=utf8 配置，然后重启数据库服务。
[root@dbsvr1 ~]# vim /etc/my.cnf //修改运行服务配置
[mysqld]
.. ..
character_set_server=utf8
[root@dbsvr1 ~]# systemctl restart mysqld //重启服务
.. ..
[root@dbsvr1 ~]# mysql –u root -p
Enter password:
.. ..
mysql> SHOW VARIABLES LIKE 'character%'; //确认更改结果
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.03 sec)
